Conduit joint and wrapper therefor



Feb. 16, 1932. V L. M. CHRISTIE 1,845,237

CONDUIT JOINT AND WRAPPER THEREFOR Filed April 9, 1931.

INVENTOR Patented Feb. 16, 1932 STATES- "PATENT- OFFICE LLEWELLYN M. CHRISTIE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T0 NATIONAL FIEEPROOFING CORPORATION, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA CONDUIT JOINT AND WRAPPER THEREFOR Application filed April 9,

The present invention relates to a conduit joint and wrapper therefor. In laying clay conduit for enclosing electric cables, a series of conduit sections are laid end to end. The joints between the abutting ends of the conduit sections are covered by strips of wrapping tape which are wound around the conduit, and then cement mortor is applied around the joints which are thus closed by the wrapping tape. The present invention relates particularly to an improved wrapping strip for this purpose, and to the joint formed thereby.

In the drawings,

Figure 1 is a perspective view showing a line of conduit embodying the present invention; and

Figure 2 is a plan view of a piece of the wrapping strip.

In the illustrated embodiment of the invention, the line of conduit consists of a number of conduit sections 1 laid end to end and having the usual ducts for carrying electric cables. The conduit sections are usually laid upon a concrete base 2. In laying the conduit the abutting ends of the section 1 are wrapped around with a piece of wrapping strip or tape 3 which covers the joint. The joint is then enclosed in a mortar joint 4. which covers and encloses the wrapping tape. The line of conduit may then be covered with a concrete protecting cap 5. The portions of the conduit sections immediately adjacent the ends are smooth, as indicated at 6. Next adjacent such smooth portions are scarified portions 7. The scarifications are provided for better bonding with the mortar of the joints 4. The width of the wrapping tape 3 is such as to overlie the smooth end portions 6, leaving the scarified portions beyond exposed. The smooth end portions allow the wrapping tape to be smoothly and tightly drawn about the abutting end portions of the conduit section.

The wrapping tape 8 is made up and furnished in long coiled strips. The wrapping tape is formed of a textile fabric, preferably a cotton sheeting known as 4.10 sheeting, having about 56 Warp and woof threads per inch. One side only of the tape is provided 1931. Serial N... 528,744.

with a waterproof adhesive coating indicated at 8 in Figure 2. The other side, indicated at 9 in Figure 2, is uncoated. Any suitable waterproof permanently adhesive coating maybe employed. Preferably the tape has and the coat applied by a calendering operation. Over these initial coats are applied three coats of a composition which is permanently adhesive, consisting of crude rubber, asphaltand ester gum, calendered on in successive layers. While this is the specific preferred manner of coating, other coatings suitably applied may be used to form upon one surface ofthetape awaterproof permanentlyfiadhesive coating. The coatings as.

thus applied, and particularly as applied in a plurality of coating layers, forms a continuous coating; which is impervious to water. silt, and the wet mortar applied over the tape.

' Sincethe tape has the adhesive coating applied to one surface only,it may be coiled into rolls of tape having the outside surface thereof formed'by the uncoated cotton fabric. As the workman uses such rolled tape, there is no tendency'for the outside of the roll to pick up dirt, as would be the case with tape adhesively coated on both sides. e

' In wrapping the tape about the conduit, the adhesive side is laid innermost to contact with and closely adhere to the glazed outside surface of the hard burned clay conduit. Since the outside surface is not coated with adhesive, the workman can wrap and press the tape against the conduit without his getting his hands smeared and sticky withthe adhesive, as would be the case with a wrapping tape having adhesive on both sides. In applying the Wrapping tape the strip of tape is laid under the conduit sections, as shown at the extreme left of Figure 1. When the next conduit section is laid to form the oint, the wrapping tape is brought up around the conduit and the ends are overlapped and pressed together, as indicated at 10' in Figure 1, so as to form a continuous wrapping around the joint.

When the mortar joint is applied over the wrapping tape, the uncoated and unsaturated body of the cotton fabric is exposed directly to the wet mortar, the water of which can enter the cotton fabric and a close bond-' ing or adherence of the mortar with the outside of the wrapping tape be obtained, which would not be the case if the fabric were impregnated with a waterproofing compound, or if its outside surface were coated with a water repellent compound.

The wrapping tape as herein described has on its inner surface next to the conduit the 7 continuous calendered-on coating of water proofing and adhesive, forming a closely adhering seal around the abutting ends of the conduit section, and preventing the entrance of green cement mortar or grout into the duct holes of the conduit, and also preventing subsequent infiltration of water, silt or sand through the tape into the duct holes of the conduit in case cracks develop in the cement mortar encasement. The provision of the adhesive on the one side only of the tape provides a tape whichvcan be wrapped and which can be handled in coils, the outside surfaces of which are not sticky, and which therefore do not tend to collect dirt; Also, the smooth and non-sticky outside surface of the tape allows the workman to wrap it conveniently around the conduit section without his hand becoming smeared with the adhesive. The nncoated outside of the fabric, in addition, provides the optimum condition of bonding the mortar with the wrapping tape.

While I have illustrated and specifically described the preferred embodiment of my invention, it is to be understood that the in vention may be otherwise embodied and practiced within the scope of the following claims.

I claim: 7

1. The combination of a series of conduit sections laid end to end, a wrapping over the joints between the sections consisting of a strip of textile fabric coated on its inner face only with a waterproofing adhesive composition, and a mortar joint covering said fabric strip and bonded to the conduit sections beyond the edges of the strip.

2. The combination of a series of conduit sections laid end to end and having smooth surface portions next their ends with scarified surface portions adjacent thereto, a wrapping over the joints between the sections consisting of a strip of textile fabric wrapped about said smooth surface portions and having its inner face only provided with a Waterproof adhesive coating, and a mortar joint covering said fabric strip and extending beyond its edges and bonded with the scarified surface portions.

3Q The combination of a series of conduit sections laid end to end, a wrapping over the joints between the sections consisting of a strip of textile fabric coated on its inner face only with a waterproof adhesive composi tion, leaving the outer face of the fabric exposed, and a mortar joint covering and bonded with the exposed face of said fabric strip and with the conduit sections beyond the edges of the strip. 7

In testimony whereof I have hereunto set my hand.

LLEWELLYN M. CHRISTIE. 

